trapan
An act of entrapping or tricking; an entrapment; also, a thing which entraps or tricks; a snare or trap; a stratagem or trick.
As for all other Pretences, they are nothing but Death and Damnation, dreſſed up in Fair VVords and Falſe Shevvs; nothing but Ginns, and Snares, and Trepans for Souls; Contrived by the Devil, and Managed by ſuch as the Devil ſets on VVork.
A person (or occasionally an animal) that traps or tricks another into doing something that benefits them but harms the victim; a fraudster, a swindler, a trickster.
archaic, obsolete
[O]ld associates who had once thought him [Richard Graham, 1st Viscount Preston] a man of dauntless courage and spotless honour, […] now pronounced that he was at best a meanspirited coward, and hinted their suspicions that he had been from the beginning a spy and a trepan.
Where it comes from
The origin of the noun is uncertain; etymology 1, noun sense 2 (“person that traps or tricks another”), the original sense, was probably thieves’ cant and may be derived from trap (noun or verb). Etymology 1, noun sense 1 (“act of entrapping or tricking; thing which entraps or tricks”) is from the verb. The verb is derived from etymology 1, noun sense 2 of the noun.
Adapted from the Wiktionary entry trapan (CC BY-SA 4.0).